21 
1913-14.] The Auditory Organ in the Cetacea. 
The auditory apparatus in the Cetacea has been modified in adaptation 
to the aquatic life of an air-breathing mammal, which can respire only 
during the relatively short period when the nasal opening or blowhole 
is above the surface of the water. There can be no doubt that the tym- 
panic cavity contains air, which it obtains during inspiration through the 
communication of its Eustachian tube with the naso-pharyngeal chamber. 
The immersion of the side of the head in the water renders unnecessary 
the development of an external auricle, capable of being turned in different 
directions to receive aerial sound waves, and the question naturally 
arises, how can sound waves be conveyed so as to impress the nerve 
apparatus in the whale’s labyrinth ? 
On this matter different opinions have been expressed. Buchanan 
considered * that the Eustachian tube and not the external meatus 
■“ conducted the pulsations of sound into the tympanum,” causing 
vibratory movements of its membrane and corresponding action in the 
chain of ossicles; whilst the meatus, through the width of its tympanic 
end, facilitated the vibratory movements of the sac-like prolongation of 
the membrane into it. This view has not, however, been accepted. 
Others have regarded the vibrations as excited by the aerial sound 
waves propagated down the external meatus, which directly impressed the 
membrane and were then conveyed by the chain of ossicles to the fenestra 
ovalis and labyrinth. As against this view it should be kept in mind that 
in the Cetacea the period is short and infrequent during which the external 
aperture is exposed to the air ; waves of sound could be transmitted only 
interm ittingly and not to much purpose. Sufficient evidence now exists 
that in the whalebone whales the meatus is blocked with a large 
plug of wax ; the lumen, therefore, cannot be occupied with air to permit 
the transmission through this medium of sound weaves. On the other 
hand, the wax-plug is a solid body closely moulded in these whales on the 
;sac-like membrane of the tympanum. As such it would doubtless transmit, 
as the cranial bones themselves can do, sound waves generated in the sur- 
rounding water, which would produce vibratory movements of the tympanic 
membrane and the chain of ossicles. In the baleen whales sufficient 
pressure exists in the air of the tympanum to produce the convex pouch- 
like projection of the membrane into the auditory meatus. 
Some years ago Claudius wrote an interesting memoir on this subject, f 
and argued that in the Cetacea the sound waves were not directly 
transmitted by the Eustachian tube, the meatus auditorius, or through 
* Op. cit. 
t Ueber das Gehororgan der Cetaceen, Kiel, 1858. 
